The victim, who is well known in the local community, had been attending a children's birthday barbecue, which started on the afternoon of 15 July and went on into the early hours of the next day.

Just after midnight, the homeless man was dancing in the park when he was approached from behind by the suspect who shot him in the left arm, left hip and right calf.

Despite his injuries, the victim managed to make his way out of the park into a nearby housing estate where he was able to get first aid and contact the emergency services. The 34-year-old then spent two weeks recovering from his injuries in hospital.

A 31-year-old man, who was arrested on 28 July on suspicion of attempted murder, has been released under investigation.

Police are now offering a £10,000 reward to anyone who can provide information which could lead to the conviction of the suspect or suspects and/or recovery of the firearm involved in the incident.

Detective Constable Shaun Pascal, of the Met's Trident and Area Crime Command, said: "This was a deplorable shooting at a children's barbecue, which left the victim with serious injuries. It is believed he will make a full recovery but the long-term effects will haunt him for many years to come.

"There are members of the public who attended the barbecue and may have witnessed this incident who could have a vital piece of information to help us piece together what happened.

"Any statements made to police will be treated in confidence. I would urge any witnesses with any information about this incident to contact us so we can bring those responsible for this crime to justice."

Any witnesses or anyone with any information about this incident is asked to call Trident detectives on 020 8217 7382 or Crimestoppers, anonymously, on 0800 555 111.